System and method for supporting inter-subnet control plane protocol for consistent multicast membership and connectivity in a high performance computing environment

ABSTRACT

Systems and methods for supporting inter subnet control plane protocol for consistent multicast membership and connectivity across multiple subnets in a high performance computing environment. In accordance with an embodiment, by associating a multicast group with an inter-subnet partition, and enforcing a dedicated router port for the multicast group, multicast loop avoidance can be provided for between connected subnets. Because only a single router port is selected as being capable of handling the MC packet, no other router port in the subnet can then pass a multicast packet back to the originating subnet.

CLAIM OF PRIORITY AND CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/414,437 entitled “SYSTEM AND METHOD FORSUPPORTING INTER SUBNET CONTROL PLANE PROTOCOL FOR CONSISTENT MULTICASTMEMBERSHIP AND CONNECTIVITY IN A HIGH PERFORMANCE COMPUTING ENVIRONMENT”filed on Jan. 24, 2017, which is incorporated by reference in itsentirety, which claims the benefit of priority to U.S. ProvisionalPatent Application entitled “SYSTEM AND METHOD FOR SUPPORTING ROUTERFEATURES IN A COMPUTING ENVIRONMENT”, Application No. 62/303,646, filedon Mar. 4, 2016, each of which applications are incorporated byreference in their entirety.

This application is related to, and incorporates by reference, U.S.Patent Application entitled “SYSTEM AND METHOD FOR SUPPORTING ROUTER SMAABSTRACTIONS FOR SMP CONNECTIVITY CHECKS ACROSS VIRTUAL ROUTER PORTS INA HIGH PERFORMANCE COMPUTING ENVIRONMENT”, application Ser. No.15/413,149, filed on Jan. 23, 2017, now U.S. Pat. No. 10,355,992.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

FIELD OF INVENTION

The present invention is generally related to computer systems, and isparticularly related to supporting inter subnet control plane protocolfor consistent multicast membership and connectivity in a highperformance computing environment.

BACKGROUND

As larger cloud computing architectures are introduced, the performanceand administrative bottlenecks associated with the traditional networkand storage have become a significant problem. There has been anincreased interest in using high performance lossless interconnects suchas InfiniBand (IB) technology as the foundation for a cloud computingfabric. This is the general area that embodiments of the invention areintended to address.

SUMMARY

Described herein are systems and methods for supporting inter-subnetcontrol plane protocol for consistent multicast membership andconnectivity in a high performance computing environment, in accordancewith an embodiment. An exemplary method for supporting multicastforwarding across multiple subnets in a high performance computingenvironment can provide, at one or more computers, including one or moremicroprocessors, a first subnet, the first subnet comprising one or moreswitches, the one or more switches comprising at least a leaf switch,wherein each of the one or more switches comprise a plurality of switchports, a plurality of end nodes, wherein the plurality of end nodes areinterconnected via the one or more switches, a subnet manager, thesubnet manager running on one of the one or more switches and theplurality of end nodes, and an inter-subnet manager, the inter-subnetmanager running on one of the one or more switches and the plurality ofend nodes. The method can configure a switch port of the plurality ofswitch ports on a switch of the one or more switches as a router port.The method can configure a second switch port of the plurality of switchports on a second switch of the one or more switches as a second routerport. The method can interconnect the first subnet with a second subnetvia both the router port and the second router port. The method can setup a multicast group within the first subnet, the multicast groupcomprising a multicast global identifier (MGID), the MGID being a memberof an inter-subnet partition (ISP).

In accordance with an embodiment, one or more host channel adapters canbe provided (in the first or second subnet or both), and can comprise atleast one virtual function, at least one virtual switch, and at leastone physical function. The plurality of end nodes (of the first orsecond subnet) can comprise physical hosts, virtual machines, or acombination of physical hosts and virtual machines, wherein the virtualmachines are associated with at least one virtual function.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an illustration of an InfiniBand environment, in accordancewith an embodiment.

FIG. 2 shows an illustration of a partitioned cluster environment, inaccordance with an embodiment

FIG. 3 shows an illustration of a tree topology in a networkenvironment, in accordance with an embodiment.

FIG. 4 shows an exemplary shared port architecture, in accordance withan embodiment.

FIG. 5 shows an exemplary vSwitch architecture, in accordance with anembodiment.

FIG. 6 shows an exemplary vPort architecture, in accordance with anembodiment.

FIG. 7 shows an exemplary vSwitch architecture with prepopulated LIDs,in accordance with an embodiment.

FIG. 8 shows an exemplary vSwitch architecture with dynamic LIDassignment, in accordance with an embodiment.

FIG. 9 shows an exemplary vSwitch architecture with vSwitch with dynamicLID assignment and prepopulated LIDs, in accordance with an embodiment.

FIG. 10 shows an exemplary multi-subnet InfiniBand fabric, in accordancewith an embodiment.

FIG. 11 shows an interconnection between two subnets in a highperformance computing environment, in accordance with an embodiment.

FIG. 12 shows an interconnection between two subnets via a dual-portvirtual router configuration in a high performance computingenvironment, in accordance with an embodiment.

FIG. 13 shows a flowchart of a method for supporting dual-port virtualrouter in a high performance computing environment, in accordance withan embodiment.

FIG. 14 illustrates a system for supporting unique multicast forwardingacross multiple subnets in a high performance computing environment, inaccordance with an embodiment.

FIG. 15 illustrates a system for supporting unique multicast forwardingacross multiple subnets in a high performance computing environment, inaccordance with an embodiment.

FIG. 16 illustrates a system for supporting unique multicast forwardingacross multiple subnets in a high performance computing environment, inaccordance with an embodiment.

FIG. 17 illustrates a system for supporting unique multicast forwardingacross multiple subnets in a high performance computing environment, inaccordance with an embodiment.

FIG. 18 is a flow chart of a method for supporting unique multicastforwarding across multiple subnets in a high performance computingenvironment, in accordance with an embodiment.

FIG. 19 illustrates a system for supporting an inter-subnet controlplane protocol for ensuring consistent multicast membership andconnectivity in a high performance computing environment, in accordancewith an embodiment.

FIG. 20 illustrates a system for supporting an inter-subnet controlplane protocol for ensuring consistent multicast membership andconnectivity in a high performance computing environment, in accordancewith an embodiment.

FIG. 21 illustrates a system for supporting an inter-subnet controlplane protocol for ensuring consistent multicast membership andconnectivity in a high performance computing environment, in accordancewith an embodiment.

FIG. 22 is a flow chart of a method for supporting multicast forwardingacross multiple subnets in a high performance computing environment.

DETAILED DESCRIPTION

The invention is illustrated, by way of example and not by way oflimitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” or “some” embodiment(s) in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone. While specific implementations are discussed, it is understood thatthe specific implementations are provided for illustrative purposesonly. A person skilled in the relevant art will recognize that othercomponents and configurations may be used without departing from thescope and spirit of the invention.

Common reference numerals can be used to indicate like elementsthroughout the drawings and detailed description; therefore, referencenumerals used in a figure may or may not be referenced in the detaileddescription specific to such figure if the element is describedelsewhere.

Described herein are systems and methods for supporting inter-subnetcontrol plane protocol for consistent multicast membership andconnectivity in a high performance computing environment, in accordancewith an embodiment.

The following description of the invention uses an InfiniBand™ (IB)network as an example for a high performance network. Throughout thefollowing description, reference can be made to the InfiniBand™specification (also referred to variously as the InfiniBandspecification, IB specification, or the legacy IB specification). Suchreference is understood to refer to the InfiniBand® Trade AssociationArchitecture Specification, Volume 1, Version 1.3, released Mar., 2015,available at http://www.inifinibandta.org, which is herein incorporatedby reference in its entirety. It will be apparent to those skilled inthe art that other types of high performance networks can be usedwithout limitation. The following description also uses the fat-treetopology as an example for a fabric topology. It will be apparent tothose skilled in the art that other types of fabric topologies can beused without limitation.

To meet the demands of the cloud in the current era (e.g., Exascaleera), it is desirable for virtual machines to be able to utilize lowoverhead network communication paradigms such as Remote Direct MemoryAccess (RDMA). RDMA bypasses the OS stack and communicates directly withthe hardware, thus, pass-through technology like Single-Root I/OVirtualization (SR-IOV) network adapters can be used. In accordance withan embodiment, a virtual switch (vSwitch) SR-IOV architecture can beprovided for applicability in high performance lossless interconnectionnetworks. As network reconfiguration time is critical to makelive-migration a practical option, in addition to network architecture,a scalable and topology-agnostic dynamic reconfiguration mechanism canbe provided.

In accordance with an embodiment, and furthermore, routing strategiesfor virtualized environments using vSwitches can be provided, and anefficient routing algorithm for network topologies (e.g., Fat-Treetopologies) can be provided. The dynamic reconfiguration mechanism canbe further tuned to minimize imposed overhead in Fat-Trees.

In accordance with an embodiment of the invention, virtualization can bebeneficial to efficient resource utilization and elastic resourceallocation in cloud computing. Live migration makes it possible tooptimize resource usage by moving virtual machines (VMs) betweenphysical servers in an application transparent manner. Thus,virtualization can enable consolidation, on-demand provisioning ofresources, and elasticity through live migration.

InfiniBand™

InfiniBand™ (IB) is an open standard lossless network technologydeveloped by the InfiniBand™ Trade Association. The technology is basedon a serial point-to-point full-duplex interconnect that offers highthroughput and low latency communication, geared particularly towardshigh-performance computing (HPC) applications and datacenters.

The InfiniBand™ Architecture (IBA) supports a two-layer topologicaldivision. At the lower layer, IB networks are referred to as subnets,where a subnet can include a set of hosts interconnected using switchesand point-to-point links. At the higher level, an IB fabric constitutesone or more subnets, which can be interconnected using routers.

Within a subnet, hosts can be connected using switches andpoint-to-point links. Additionally, there can be a master managemententity, the subnet manager (SM), which resides on a designated device inthe subnet. The subnet manager is responsible for configuring,activating and maintaining the IB subnet. Additionally, the subnetmanager (SM) can be responsible for performing routing tablecalculations in an IB fabric. Here, for example, the routing of the IBnetwork aims at proper load balancing between all source and destinationpairs in the local subnet.

Through the subnet management interface, the subnet manager exchangescontrol packets, which are referred to as subnet management packets(SMPs), with subnet management agents (SMAs). The subnet managementagents reside on every IB subnet device. By using SMPs, the subnetmanager is able to discover the fabric, configure end nodes andswitches, and receive notifications from SMAs.

In accordance with an embodiment, intra-subnet routing in an IB networkcan be based on linear forwarding tables (LFTs) stored in the switches.The LFTs are calculated by the SM according to the routing mechanism inuse. In a subnet, Host Channel Adapter (HCA) ports on the end nodes andswitches are addressed using local identifiers (LIDs). Each entry in alinear forwarding table (LFT) consists of a destination LID (DLID) andan output port. Only one entry per LID in the table is supported. When apacket arrives at a switch, its output port is determined by looking upthe DLID in the forwarding table of the switch. The routing isdeterministic as packets take the same path in the network between agiven source-destination pair (LID pair).

Generally, all other subnet managers, excepting the master subnetmanager, act in standby mode for fault-tolerance. In a situation where amaster subnet manager fails, however, a new master subnet manager isnegotiated by the standby subnet managers. The master subnet manageralso performs periodic sweeps of the subnet to detect any topologychanges and reconfigure the network accordingly.

Furthermore, hosts and switches within a subnet can be addressed usinglocal identifiers (LIDs), and a single subnet can be limited to 49151unicast LIDs. Besides the LIDs, which are the local addresses that arevalid within a subnet, each IB device can have a 64-bit global uniqueidentifier (GUID). A GUID can be used to form a global identifier (GID),which is an IB layer three (L3) address.

The SM can calculate routing tables (i.e., the connections/routesbetween each pair of nodes within the subnet) at network initializationtime. Furthermore, the routing tables can be updated whenever thetopology changes, in order to ensure connectivity and optimalperformance. During normal operations, the SM can perform periodic lightsweeps of the network to check for topology changes. If a change isdiscovered during a light sweep or if a message (trap) signaling anetwork change is received by the SM, the SM can reconfigure the networkaccording to the discovered changes.

For example, the SM can reconfigure the network when the networktopology changes, such as when a link goes down, when a device is added,or when a link is removed. The reconfiguration steps can include thesteps performed during the network initialization. Furthermore, thereconfigurations can have a local scope that is limited to the subnets,in which the network changes occurred. Also, the segmenting of a largefabric with routers may limit the reconfiguration scope.

An example InfiniBand fabric is shown in FIG. 1, which shows anillustration of an InfiniBand environment 100, in accordance with anembodiment. In the example shown in FIG. 1, nodes A-E, 101-105, use theInfiniBand fabric, 120, to communicate, via the respective host channeladapters 111-115. In accordance with an embodiment, the various nodes,e.g., nodes A-E, 101-105, can be represented by various physicaldevices. In accordance with an embodiment, the various nodes, e.g.,nodes A-E, 101-105, can be represented by various virtual devices, suchas virtual machines.

Partitioning in InfiniBand

In accordance with an embodiment, IB networks can support partitioningas a security mechanism to provide for isolation of logical groups ofsystems sharing a network fabric. Each HCA port on a node in the fabriccan be a member of one or more partitions. Partition memberships aremanaged by a centralized partition manager, which can be part of the SM.The SM can configure partition membership information on each port as atable of 16-bit partition keys (P_Keys). The SM can also configureswitch and router ports with the partition enforcement tables containingP_Key information associated with the end-nodes that send or receivedata traffic through these ports. Additionally, in a general case,partition membership of a switch port can represent a union of allmembership indirectly associated with LIDs routed via the port in anegress (towards the link) direction.

In accordance with an embodiment, partitions are logical groups of portssuch that the members of a group can only communicate to other membersof the same logical group. At host channel adapters (HCAs) and switches,packets can be filtered using the partition membership information toenforce isolation. Packets with invalid partitioning information can bedropped as soon as the packets reaches an incoming port. In partitionedIB systems, partitions can be used to create tenant clusters. Withpartition enforcement in place, a node cannot communicate with othernodes that belong to a different tenant cluster. In this way, thesecurity of the system can be guaranteed even in the presence ofcompromised or malicious tenant nodes.

In accordance with an embodiment, for the communication between nodes,Queue Pairs (QPs) and End-to-End contexts (EECs) can be assigned to aparticular partition, except for the management Queue Pairs (QP0 andQP1). The P_Key information can then be added to every IB transportpacket sent. When a packet arrives at an HCA port or a switch, its P_Keyvalue can be validated against a table configured by the SM. If aninvalid P_Key value is found, the packet is discarded immediately. Inthis way, communication is allowed only between ports sharing apartition.

An example of IB partitions is shown in FIG. 2, which shows anillustration of a partitioned cluster environment, in accordance with anembodiment. In the example shown in FIG. 2, nodes A-E, 101-105, use theInfiniBand fabric, 120, to communicate, via the respective host channeladapters 111-115. The nodes A-E are arranged into partitions, namelypartition 1, 130, partition 2, 140, and partition 3, 150. Partition 1comprises node A 101 and node D 104. Partition 2 comprises node A 101,node B 102, and node C 103. Partition 3 comprises node C 103 and node E105. Because of the arrangement of the partitions, node D 104 and node E105 are not allowed to communicate as these nodes do not share apartition. Meanwhile, for example, node A 101 and node C 103 are allowedto communicate as these nodes are both members of partition 2, 140.

Virtual Machines in InfiniBand

During the last decade, the prospect of virtualized High PerformanceComputing (HPC) environments has improved considerably as CPU overheadhas been practically removed through hardware virtualization support;memory overhead has been significantly reduced by virtualizing theMemory Management Unit; storage overhead has been reduced by the use offast SAN storages or distributed networked file systems; and network I/Ooverhead has been reduced by the use of device passthrough techniqueslike Single Root Input/Output Virtualization (SR-IOV). It is nowpossible for clouds to accommodate virtual HPC (vHPC) clusters usinghigh performance interconnect solutions and deliver the necessaryperformance.

However, when coupled with lossless networks, such as InfiniBand (IB),certain cloud functionality, such as live migration of virtual machines(VMs), still remains an issue due to the complicated addressing androuting schemes used in these solutions. IB is an interconnectionnetwork technology offering high bandwidth and low latency, thus, isvery well suited for HPC and other communication intensive workloads.

The traditional approach for connecting IB devices to VMs is byutilizing SR-IOV with direct assignment. However, achieving livemigration of VMs assigned with IB Host Channel Adapters (HCAs) usingSR-IOV has proved to be challenging. Each IB connected node has threedifferent addresses: LID, GUID, and GID. When a live migration happens,one or more of these addresses change. Other nodes communicating withthe VM-in-migration can lose connectivity. When this happens, the lostconnection can be attempted to be renewed by locating the virtualmachine's new address to reconnect to by sending Subnet Administration(SA) path record queries to the IB Subnet Manager (SM).

IB uses three different types of addresses. A first type of address isthe 16 bits Local Identifier (LID). At least one unique LID is assignedto each HCA port and each switch by the SM. The LIDs are used to routetraffic within a subnet. Since the LID is 16 bits long, 65536 uniqueaddress combinations can be made, of which only 49151 (0x0001-0xBFFF)can be used as unicast addresses. Consequently, the number of availableunicast addresses defines the maximum size of an IB subnet. A secondtype of address is the 64 bits Global Unique Identifier (GUID) assignedby the manufacturer to each device (e.g. HCAs and switches) and each HCAport. The SM may assign additional subnet unique GUIDs to an HCA port,which is useful when SR-IOV is used. A third type of address is the 128bits Global Identifier (GID). The GID is a valid IPv6 unicast address,and at least one is assigned to each HCA port. The GID is formed bycombining a globally unique 64 bits prefix assigned by the fabricadministrator, and the GUID address of each HCA port.

Fat-Tree (FTree) Topologies and Routing

In accordance with an embodiment, some of the IB based HPC systemsemploy a fat-tree topology to take advantage of the useful propertiesfat-trees offer. These properties include full bisection-bandwidth andinherent fault-tolerance due to the availability of multiple pathsbetween each source destination pair. The initial idea behind fat-treeswas to employ fatter links between nodes, with more available bandwidth,as the tree moves towards the roots of the topology. The fatter linkscan help to avoid congestion in the upper-level switches and thebisection-bandwidth is maintained.

FIG. 3 shows an illustration of a tree topology in a networkenvironment, in accordance with an embodiment. As shown in FIG. 3, oneor more end nodes 201-204 can be connected in a network fabric 200. Thenetwork fabric 200 can be based on a fat-tree topology, which includes aplurality of leaf switches 211-214, and multiple spine switches or rootswitches 231-234. Additionally, the network fabric 200 can include oneor more intermediate switches, such as switches 221-224.

Also as shown in FIG. 3, each of the end nodes 201-204 can be amulti-homed node, i.e., a single node that is connected to two or moreparts of the network fabric 200 through multiple ports. For example, thenode 201 can include the ports H1 and H2, the node 202 can include theports H3 and H4, the node 203 can include the ports H5 and H6, and thenode 204 can include the ports H7 and H8.

Additionally, each switch can have multiple switch ports. For example,the root switch 231 can have the switch ports 1-2, the root switch 232can have the switch ports 3-4, the root switch 233 can have the switchports 5-6, and the root switch 234 can have the switch ports 7-8.

In accordance with an embodiment, the fat-tree routing mechanism is oneof the most popular routing algorithm for IB based fat-tree topologies.The fat-tree routing mechanism is also implemented in the OFED (OpenFabric Enterprise Distribution—a standard software stack for buildingand deploying IB based applications) subnet manager, OpenSM.

The fat-tree routing mechanism aims to generate LFTs that evenly spreadshortest-path routes across the links in the network fabric. Themechanism traverses the fabric in the indexing order and assigns targetLIDs of the end nodes, and thus the corresponding routes, to each switchport. For the end nodes connected to the same leaf switch, the indexingorder can depend on the switch port to which the end node is connected(i.e., port numbering sequence). For each port, the mechanism canmaintain a port usage counter, and can use this port usage counter toselect a least-used port each time a new route is added.

In accordance with an embodiment, in a partitioned subnet, nodes thatare not members of a common partition are not allowed to communicate.Practically, this means that some of the routes assigned by the fat-treerouting algorithm are not used for the user traffic. The problem ariseswhen the fat tree routing mechanism generates LFTs for those routes thesame way it does for the other functional paths. This behavior canresult in degraded balancing on the links, as nodes are routed in theorder of indexing. As routing can be performed oblivious to thepartitions, fat-tree routed subnets, in general, provide poor isolationamong partitions.

In accordance with an embodiment, a Fat-Tree is a hierarchical networktopology that can scale with the available network resources. Moreover,Fat-Trees are easy to build using commodity switches placed on differentlevels of the hierarchy. Different variations of Fat-Trees are commonlyavailable, including k-ary-n-trees, Extended Generalized Fat-Trees(XGFTs), Parallel Ports Generalized Fat-Trees (PGFTs) and Real LifeFat-Trees (RLFTs).

A k-ary-n-tree is an n level Fat-Tree with k^(n) end nodes and n·k^(n-1)switches, each with 2 k ports. Each switch has an equal number of up anddown connections in the tree. XGFT Fat-Tree extends k-ary-n-trees byallowing both different number of up and down connections for theswitches, and different number of connections at each level in the tree.The PGFT definition further broadens the XGFT topologies and permitsmultiple connections between switches. A large variety of topologies canbe defined using XGFTs and PGFTs. However, for practical purposes, RLFT,which is a restricted version of PGFT, is introduced to define Fat-Treescommonly found in today's HPC clusters. An RLFT uses the same port-countswitches at all levels in the Fat-Tree.

Input/Output (I/O) Virtualization

In accordance with an embodiment, I/O Virtualization (IOV) can provideavailability of I/O by allowing virtual machines (VMs) to access theunderlying physical resources. The combination of storage traffic andinter-server communication impose an increased load that may overwhelmthe I/O resources of a single server, leading to backlogs and idleprocessors as they are waiting for data. With the increase in number ofI/O requests, IOV can provide availability; and can improve performance,scalability and flexibility of the (virtualized) I/O resources to matchthe level of performance seen in modern CPU virtualization.

In accordance with an embodiment, IOV is desired as it can allow sharingof I/O resources and provide protected access to the resources from theVMs. IOV decouples a logical device, which is exposed to a VM, from itsphysical implementation. Currently, there can be different types of IOVtechnologies, such as emulation, paravirtualization, direct assignment(DA), and single root-I/O virtualization (SR-IOV).

In accordance with an embodiment, one type of IOV technology is softwareemulation. Software emulation can allow for a decoupledfront-end/back-end software architecture. The front-end can be a devicedriver placed in the VM, communicating with the back-end implemented bya hypervisor to provide I/O access. The physical device sharing ratio ishigh and live migrations of VMs are possible with just a fewmilliseconds of network downtime. However, software emulation introducesadditional, undesired computational overhead.

In accordance with an embodiment, another type of IOV technology isdirect device assignment. Direct device assignment involves a couplingof I/O devices to VMs, with no device sharing between VMs. Directassignment, or device passthrough, provides near to native performancewith minimum overhead. The physical device bypasses the hypervisor andis directly attached to the VM. However, a downside of such directdevice assignment is limited scalability, as there is no sharing amongvirtual machines—one physical network card is coupled with one VM.

In accordance with an embodiment, Single Root IOV (SR-IOV) can allow aphysical device to appear through hardware virtualization as multipleindependent lightweight instances of the same device. These instancescan be assigned to VMs as passthrough devices, and accessed as VirtualFunctions (VFs). The hypervisor accesses the device through a unique(per device), fully featured Physical Function (PF). SR-IOV eases thescalability issue of pure direct assignment. However, a problempresented by SR-IOV is that it can impair VM migration. Among these IOVtechnologies, SR-IOV can extend the PCI Express (PCIe) specificationwith the means to allow direct access to a single physical device frommultiple VMs while maintaining near to native performance. Thus, SR-IOVcan provide good performance and scalability.

SR-IOV allows a PCIe device to expose multiple virtual devices that canbe shared between multiple guests by allocating one virtual device toeach guest. Each SR-IOV device has at least one physical function (PF)and one or more associated virtual functions (VF). A PF is a normal PCIefunction controlled by the virtual machine monitor (VMM), or hypervisor,whereas a VF is a light-weight PCIe function. Each VF has its own baseaddress (BAR) and is assigned with a unique requester ID that enablesI/O memory management unit (IOMMU) to differentiate between the trafficstreams to/from different VFs. The IOMMU also apply memory and interrupttranslations between the PF and the VFs.

Unfortunately, however, direct device assignment techniques pose abarrier for cloud providers in situations where transparent livemigration of virtual machines is desired for data center optimization.The essence of live migration is that the memory contents of a VM arecopied to a remote hypervisor. Then the VM is paused at the sourcehypervisor, and the VM's operation is resumed at the destination. Whenusing software emulation methods, the network interfaces are virtual sotheir internal states are stored into the memory and get copied as well.Thus the downtime could be brought down to a few milliseconds.

However, migration becomes more difficult when direct device assignmenttechniques, such as SR-IOV, are used. In such situations, a completeinternal state of the network interface cannot be copied as it is tiedto the hardware. The SR-IOV VFs assigned to a VM are instead detached,the live migration will run, and a new VF will be attached at thedestination. In the case of InfiniBand and SR-IOV, this process canintroduce downtime in the order of seconds. Moreover, in an SR-IOVshared port model the addresses of the VM will change after themigration, causing additional overhead in the SM and a negative impacton the performance of the underlying network fabric.

InfiniBand SR-IOV Architecture—Shared Port

There can be different types of SR-IOV models, e.g. a shared port model,a virtual switch model, and a virtual port model.

FIG. 4 shows an exemplary shared port architecture, in accordance withan embodiment. As depicted in the figure, a host 300 (e.g., a hostchannel adapter) can interact with a hypervisor 310, which can assignthe various virtual functions 330, 340, 350, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 310.

In accordance with an embodiment, when using a shared port architecture,such as that depicted in FIG. 4, the host, e.g., HCA, appears as asingle port in the network with a single shared LID and shared QueuePair (QP) space between the physical function 320 and the virtualfunctions 330, 350, 350. However, each function (i.e., physical functionand virtual functions) can have their own GID.

As shown in FIG. 4, in accordance with an embodiment, different GIDs canbe assigned to the virtual functions and the physical function, and thespecial queue pairs, QP0 and QP1 (i.e., special purpose queue pairs thatare used for InfiniBand management packets), are owned by the physicalfunction. These QPs are exposed to the VFs as well, but the VFs are notallowed to use QP0 (all SMPs coming from VFs towards QP0 are discarded),and QP1 can act as a proxy of the actual QP1 owned by the PF.

In accordance with an embodiment, the shared port architecture can allowfor highly scalable data centers that are not limited by the number ofVMs (which attach to the network by being assigned to the virtualfunctions), as the LID space is only consumed by physical machines andswitches in the network.

However, a shortcoming of the shared port architecture is the inabilityto provide transparent live migration, hindering the potential forflexible VM placement. As each LID is associated with a specifichypervisor, and shared among all VMs residing on the hypervisor, amigrating VM (i.e., a virtual machine migrating to a destinationhypervisor) has to have its LID changed to the LID of the destinationhypervisor. Furthermore, as a consequence of the restricted QP0 access,a subnet manager cannot run inside a VM.

InfiniBand SR-IOV Architecture Models—Virtual Switch (vSwitch)

FIG. 5 shows an exemplary vSwitch architecture, in accordance with anembodiment. As depicted in the figure, a host 400 (e.g., a host channeladapter) can interact with a hypervisor 410, which can assign thevarious virtual functions 430, 440, 450, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 410. A virtual switch 415 can also be handled by thehypervisor 401.

In accordance with an embodiment, in a vSwitch architecture each virtualfunction 430, 440, 450 is a complete virtual Host Channel Adapter(vHCA), meaning that the VM assigned to a VF is assigned a complete setof IB addresses (e.g., GID, GUID, LID) and a dedicated QP space in thehardware. For the rest of the network and the SM, the HCA 400 looks likea switch, via the virtual switch 415, with additional nodes connected toit. The hypervisor 410 can use the PF 420, and the VMs (attached to thevirtual functions) use the VFs.

In accordance with an embodiment, a vSwitch architecture providetransparent virtualization. However, because each virtual function isassigned a unique LID, the number of available LIDs gets consumedrapidly. As well, with many LID addresses in use (i.e., one each foreach physical function and each virtual function), more communicationpaths have to be computed by the SM and more Subnet Management Packets(SMPs) have to be sent to the switches in order to update their LFTs.For example, the computation of the communication paths might takeseveral minutes in large networks. Because LID space is limited to 49151unicast LIDs, and as each VM (via a VF), physical node, and switchoccupies one LID each, the number of physical nodes and switches in thenetwork limits the number of active VMs, and vice versa.

InfiniBand SR-IOV Architecture Models—Virtual Port (vPort)

FIG. 6 shows an exemplary vPort concept, in accordance with anembodiment. As depicted in the figure, a host 300 (e.g., a host channeladapter) can interact with a hypervisor 410, which can assign thevarious virtual functions 330, 340, 350, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 310.

In accordance with an embodiment, the vPort concept is loosely definedin order to give freedom of implementation to vendors (e.g. thedefinition does not rule that the implementation has to be SRIOVspecific), and a goal of the vPort is to standardize the way VMs arehandled in subnets. With the vPort concept, both SR-IOV Shared-Port-likeand vSwitch-like architectures or a combination of both, that can bemore scalable in both the space and performance domains, can be defined.A vPort supports optional LIDs, and unlike the Shared-Port, the SM isaware of all the vPorts available in a subnet even if a vPort is notusing a dedicated LID.

InfiniBand SR-IOV Architecture Models—vSwitch with Prepopulated LIDs

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with prepopulatedLIDs.

FIG. 7 shows an exemplary vSwitch architecture with prepopulated LIDs,in accordance with an embodiment. As depicted in the figure, a number ofswitches 501-504 can provide communication within the network switchedenvironment 600 (e.g., an IB subnet) between members of a fabric, suchas an InfiniBand fabric. The fabric can include a number of hardwaredevices, such as host channel adapters 510, 520, 530. Each of the hostchannel adapters 510, 520, 530, can in turn interact with a hypervisor511, 521, and 531, respectively. Each hypervisor can, in turn, inconjunction with the host channel adapter it interacts with, setup andassign a number of virtual functions 514, 515, 516, 524, 525, 526, 534,535, 536, to a number of virtual machines. For example, virtual machine1 550 can be assigned by the hypervisor 511 to virtual function 1 514.Hypervisor 511 can additionally assign virtual machine 2 551 to virtualfunction 2 515, and virtual machine 3 552 to virtual function 3 516.Hypervisor 531 can, in turn, assign virtual machine 4 553 to virtualfunction 1 534. The hypervisors can access the host channel adaptersthrough a fully featured physical function 513, 523, 533, on each of thehost channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 600.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with prepopulatedLIDs. Referring to FIG. 7, the LIDs are prepopulated to the variousphysical functions 513, 523, 533, as well as the virtual functions514-516, 524-526, 534-536 (even those virtual functions not currentlyassociated with an active virtual machine). For example, physicalfunction 513 is prepopulated with LID 1, while virtual function 1 534 isprepopulated with LID 10. The LIDs are prepopulated in an SR-IOVvSwitch-enabled subnet when the network is booted. Even when not all ofthe VFs are occupied by VMs in the network, the populated VFs areassigned with a LID as shown in FIG. 7.

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

In accordance with an embodiment, in a vSwitch architecture withprepopulated LIDs, each hypervisor can consume one LID for itselfthrough the PF and one more LID for each additional VF. The sum of allthe VFs available in all hypervisors in an IB subnet, gives the maximumamount of VMs that are allowed to run in the subnet. For example, in anIB subnet with 16 virtual functions per hypervisor in the subnet, theneach hypervisor consumes 17 LIDs (one LID for each of the 16 virtualfunctions plus one LID for the physical function) in the subnet. In suchan IB subnet, the theoretical hypervisor limit for a single subnet isruled by the number of available unicast LIDs and is: 2891 (49151available LIDs divided by 17 LIDs per hypervisor), and the total numberof VMs (i.e., the limit) is 46256 (2891 hypervisors times 16 VFs perhypervisor). (In actuality, these numbers are actually smaller sinceeach switch, router, or dedicated SM node in the IB subnet consumes aLID as well). Note that the vSwitch does not need to occupy anadditional LID as it can share the LID with the PF

In accordance with an embodiment, in a vSwitch architecture withprepopulated LIDs, communication paths are computed for all the LIDs thefirst time the network is booted. When a new VM needs to be started thesystem does not have to add a new LID in the subnet, an action thatwould otherwise cause a complete reconfiguration of the network,including path recalculation, which is the most time consuming part.Instead, an available port for a VM is located (i.e., an availablevirtual function) in one of the hypervisors and the virtual machine isattached to the available virtual function.

In accordance with an embodiment, a vSwitch architecture withprepopulated LIDs also allows for the ability to calculate and usedifferent paths to reach different VMs hosted by the same hypervisor.Essentially, this allows for such subnets and networks to use a LID MaskControl (LMC) like feature to provide alternative paths towards onephysical machine, without being bound by the limitation of the LMC thatrequires the LIDs to be sequential. The freedom to use non-sequentialLIDs is particularly useful when a VM needs to be migrated and carry itsassociated LID to the destination.

In accordance with an embodiment, along with the benefits shown above ofa vSwitch architecture with prepopulated LIDs, certain considerationscan be taken into account. For example, because the LIDs areprepopulated in an SR-IOV vSwitch-enabled subnet when the network isbooted, the initial path computation (e.g., on boot-up) can take longerthan if the LIDs were not pre-populated.

InfiniBand SR-IOV Architecture Models—vSwitch with Dynamic LIDAssignment

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with dynamic LIDassignment.

FIG. 8 shows an exemplary vSwitch architecture with dynamic LIDassignment, in accordance with an embodiment. As depicted in the figure,a number of switches 501-504 can provide communication within thenetwork switched environment 700 (e.g., an IB subnet) between members ofa fabric, such as an InfiniBand fabric. The fabric can include a numberof hardware devices, such as host channel adapters 510, 520, 530. Eachof the host channel adapters 510, 520, 530, can in turn interact with ahypervisor 511, 521, 531, respectively. Each hypervisor can, in turn, inconjunction with the host channel adapter it interacts with, setup andassign a number of virtual functions 514, 515, 516, 524, 525, 526, 534,535, 536, to a number of virtual machines. For example, virtual machine1 550 can be assigned by the hypervisor 511 to virtual function 1 514.Hypervisor 511 can additionally assign virtual machine 2 551 to virtualfunction 2 515, and virtual machine 3 552 to virtual function 3 516.Hypervisor 531 can, in turn, assign virtual machine 4 553 to virtualfunction 1 534. The hypervisors can access the host channel adaptersthrough a fully featured physical function 513, 523, 533, on each of thehost channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 700.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with dynamic LIDassignment. Referring to FIG. 8, the LIDs are dynamically assigned tothe various physical functions 513, 523, 533, with physical function 513receiving LID 1, physical function 523 receiving LID 2, and physicalfunction 533 receiving LID 3. Those virtual functions that areassociated with an active virtual machine can also receive a dynamicallyassigned LID. For example, because virtual machine 1 550 is active andassociated with virtual function 1 514, virtual function 514 can beassigned LID 5. Likewise, virtual function 2 515, virtual function 3516, and virtual function 1 534 are each associated with an activevirtual function. Because of this, these virtual functions are assignedLIDs, with LID 7 being assigned to virtual function 2 515, LID 11 beingassigned to virtual function 3 516, and LID 9 being assigned to virtualfunction 1 534. Unlike vSwitch with prepopulated LIDs, those virtualfunctions not currently associated with an active virtual machine do notreceive a LID assignment.

In accordance with an embodiment, with the dynamic LID assignment, theinitial path computation can be substantially reduced. When the networkis booting for the first time and no VMs are present then a relativelysmall number of LIDs can be used for the initial path calculation andLFT distribution.

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

In accordance with an embodiment, when a new VM is created in a systemutilizing vSwitch with dynamic LID assignment, a free VM slot is foundin order to decide on which hypervisor to boot the newly added VM, and aunique non-used unicast LID is found as well. However, there are noknown paths in the network and the LFTs of the switches for handling thenewly added LID. Computing a new set of paths in order to handle thenewly added VM is not desirable in a dynamic environment where severalVMs may be booted every minute. In large IB subnets, computing a new setof routes can take several minutes, and this procedure would have torepeat each time a new VM is booted.

Advantageously, in accordance with an embodiment, because all the VFs ina hypervisor share the same uplink with the PF, there is no need tocompute a new set of routes. It is only needed to iterate through theLFTs of all the physical switches in the network, copy the forwardingport from the LID entry that belongs to the PF of the hypervisor—wherethe VM is created—to the newly added LID, and send a single SMP toupdate the corresponding LFT block of the particular switch. Thus thesystem and method avoids the need to compute a new set of routes.

In accordance with an embodiment, the LIDs assigned in the vSwitch withdynamic LID assignment architecture do not have to be sequential. Whencomparing the LIDs assigned on VMs on each hypervisor in vSwitch withprepopulated LIDs versus vSwitch with dynamic LID assignment, it isnotable that the LIDs assigned in the dynamic LID assignmentarchitecture are non-sequential, while those prepopulated in aresequential in nature. In the vSwitch dynamic LID assignmentarchitecture, when a new VM is created, the next available LID is usedthroughout the lifetime of the VM. Conversely, in a vSwitch withprepopulated LIDs, each VM inherits the LID that is already assigned tothe corresponding VF, and in a network without live migrations, VMsconsecutively attached to a given VF get the same LID.

In accordance with an embodiment, the vSwitch with dynamic LIDassignment architecture can resolve the drawbacks of the vSwitch withprepopulated LIDs architecture model at a cost of some additionalnetwork and runtime SM overhead. Each time a VM is created, the LFTs ofthe physical switches in the subnet are updated with the newly added LIDassociated with the created VM. One subnet management packet (SMP) perswitch is needed to be sent for this operation. The LMC-likefunctionality is also not available, because each VM is using the samepath as its host hypervisor. However, there is no limitation on thetotal amount of VFs present in all hypervisors, and the number of VFsmay exceed that of the unicast LID limit. Of course, not all of the VFsare allowed to be attached on active VMs simultaneously if this is thecase, but having more spare hypervisors and VFs adds flexibility fordisaster recovery and optimization of fragmented networks when operatingclose to the unicast LID limit.

InfiniBand SR-IOV Architecture Models—vSwitch with Dynamic LIDAssignment and Prepopulated LIDs

FIG. 9 shows an exemplary vSwitch architecture with vSwitch with dynamicLID assignment and prepopulated LIDs, in accordance with an embodiment.As depicted in the figure, a number of switches 501-504 can providecommunication within the network switched environment 800 (e.g., an IBsubnet) between members of a fabric, such as an InfiniBand fabric. Thefabric can include a number of hardware devices, such as host channeladapters 510, 520, 530. Each of the host channel adapters 510, 520, 530,can in turn interact with a hypervisor 511, 521, and 531, respectively.Each hypervisor can, in turn, in conjunction with the host channeladapter it interacts with, setup and assign a number of virtualfunctions 514, 515, 516, 524, 525, 526, 534, 535, 536, to a number ofvirtual machines. For example, virtual machine 1 550 can be assigned bythe hypervisor 511 to virtual function 1 514. Hypervisor 511 canadditionally assign virtual machine 2 551 to virtual function 2 515.Hypervisor 521 can assign virtual machine 3 552 to virtual function 3526. Hypervisor 531 can, in turn, assign virtual machine 4 553 tovirtual function 2 535. The hypervisors can access the host channeladapters through a fully featured physical function 513, 523, 533, oneach of the host channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 800.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a hybrid vSwitch architecture withdynamic LID assignment and prepopulated LIDs. Referring to FIG. 9,hypervisor 511 can be arranged with vSwitch with prepopulated LIDsarchitecture, while hypervisor 521 can be arranged with vSwitch withprepopulated LIDs and dynamic LID assignment. Hypervisor 531 can bearranged with vSwitch with dynamic LID assignment. Thus, the physicalfunction 513 and virtual functions 514-516 have their LIDs prepopulated(i.e., even those virtual functions not attached to an active virtualmachine are assigned a LID). Physical function 523 and virtual function1 524 can have their LIDs prepopulated, while virtual function 2 and 3,525 and 526, have their LIDs dynamically assigned (i.e., virtualfunction 2 525 is available for dynamic LID assignment, and virtualfunction 3 526 has a LID of 11 dynamically assigned as virtual machine 3552 is attached). Finally, the functions (physical function and virtualfunctions) associated with hypervisor 3 531 can have their LIDsdynamically assigned. This results in virtual functions 1 and 3, 534 and536, are available for dynamic LID assignment, while virtual function 2535 has LID of 9 dynamically assigned as virtual machine 4 553 isattached there.

In accordance with an embodiment, such as that depicted in FIG. 9, whereboth vSwitch with prepopulated LIDs and vSwitch with dynamic LIDassignment are utilized (independently or in combination within anygiven hypervisor), the number of prepopulated LIDs per host channeladapter can be defined by a fabric administrator and can be in the rangeof 0<=prepopulated VFs<=Total VFs (per host channel adapter), and theVFs available for dynamic LID assignment can be found by subtracting thenumber of prepopulated VFs from the total number of VFs (per hostchannel adapter).

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

InfiniBand—Inter-Subnet Communication (Fabric Manager)

In accordance with an embodiment, in addition to providing an InfiniBandfabric within a single subnet, embodiments of the current disclosure canalso provide for an InfiniBand fabric that spans two or more subnets.

FIG. 10 shows an exemplary multi-subnet InfiniBand fabric, in accordancewith an embodiment. As depicted in the figure, within subnet A 1000, anumber of switches 1001-1004 can provide communication within subnet A1000 (e.g., an IB subnet) between members of a fabric, such as anInfiniBand fabric. The fabric can include a number of hardware devices,such as, for example, channel adapter 1010. Host channel adapter 1010can in turn interact with a hypervisor 1011. The hypervisor can, inturn, in conjunction with the host channel adapter it interacts with,setup a number of virtual functions 1014. The hypervisor canadditionally assign virtual machines to each of the virtual functions,such as virtual machine 1 1015 being assigned to virtual function 11014. The hypervisor can access their associated host channel adaptersthrough a fully featured physical function, such as physical function1013, on each of the host channel adapters. Within subnet B 1040, anumber of switches 1021-1024 can provide communication within subnet B1040 (e.g., an IB subnet) between members of a fabric, such as anInfiniBand fabric. The fabric can include a number of hardware devices,such as, for example, channel adapter 1030. Host channel adapter 1030can in turn interact with a hypervisor 1031. The hypervisor can, inturn, in conjunction with the host channel adapter it interacts with,setup a number of virtual functions 1034. The hypervisor canadditionally assign virtual machines to each of the virtual functions,such as virtual machine 2 1035 being assigned to virtual function 21034. The hypervisor can access their associated host channel adaptersthrough a fully featured physical function, such as physical function1033, on each of the host channel adapters. It is noted that althoughonly one host channel adapter is shown within each subnet (i.e., subnetA and subnet B), it is to be understood that a plurality of host channeladapters, and their corresponding components, can be included withineach subnet.

In accordance with an embodiment, each of the host channel adapters canadditionally be associated with a virtual switch, such as virtual switch1012 and virtual switch 1032, and each HCA can be set up with adifferent architecture model, as discussed above. Although both subnetswithin FIG. 10 are shown as using a vSwitch with prepopulated LIDarchitecture model, this is not meant to imply that all such subnetconfigurations must follow a similar architecture model.

In accordance with an embodiment, at least one switch within each subnetcan be associated with a router, such as switch 1002 within subnet A1000 being associated with router 1005, and switch 1021 within subnet B1040 being associated with router 1006.

In accordance with an embodiment, at least one device (e.g., a switch, anode . . . etc.) can be associated with a fabric manager (not shown).The fabric manager can be used, for example, to discover inter-subnetfabric topology, create a fabric profile (e.g., a virtual machine fabricprofile), build virtual machine related database objects that forms thebasis for building a virtual machine fabric profile. In addition, thefabric manager can define legal inter-subnet connectivity in terms ofwhich subnets are allowed to communicate via which router ports usingwhich partition numbers.

In accordance with an embodiment, when traffic at an originating source,such as virtual machine 1 within subnet A, is addressed to a destinationin a different subnet, such as virtual machine 2 within subnet B, thetraffic can be addressed to the router within subnet A, i.e., router1005, which can then pass the traffic to subnet B via its link withrouter 1006.

Virtual Dual Port Router

In accordance with an embodiment, a dual port router abstraction canprovide a simple way for enabling subnet-to-subnet router functionalityto be defined based on a switch hardware implementation that has theability to do GRH (global route header) to LRH (local route header)conversion in addition to performing normal LRH based switching.

In accordance with an embodiment, a virtual dual-port router canlogically be connected outside a corresponding switch port. This virtualdual-port router can provide an InfiniBand specification compliant viewto a standard management entity, such as a Subnet Manager.

In accordance with an embodiment, a dual-ported router model impliesthat different subnets can be connected in a way where each subnet fullycontrols the forwarding of packets as well as address mappings in theingress path to the subnet, and without impacting the routing andlogical connectivity within either of the incorrectly connected subnets.

In accordance with an embodiment, in a situation involving anincorrectly connected fabric, the use of a virtual dual-port routerabstraction can also allow a management entity, such as a Subnet Managerand IB diagnostic software, to behave correctly in the presence ofun-intended physical connectivity to a remote subnet.

FIG. 11 shows an interconnection between two subnets in a highperformance computing environment, in accordance with an embodiment.Prior to configuration with a virtual dual port router, a switch 1120 insubnet A 1101 can be connected through a switch port 1121 of switch1120, via a physical connection 1110, to a switch 1130 in subnet B 1102,via a switch port 1131 of switch 1130. In such an embodiment, eachswitch port, 1121 and 1131, can act both as switch ports and routerports.

In accordance with an embodiment, a problem with this configuration isthat a management entity, such as a subnet manager in an InfiniBandsubnet, cannot distinguish between a physical port that is both a switchport and a router port. In such a situation, a SM can treat the switchport as having a router port connected to that switch port. But if theswitch port is connected to another subnet, via, for example, a physicallink, with another subnet manager, then the subnet manager can be ableto send a discovery message out on the physical link. However, such adiscovery message cannot be allowed at the other subnet.

FIG. 12 shows an interconnection between two subnets via a dual-portvirtual router configuration in a high performance computingenvironment, in accordance with an embodiment.

In accordance with an embodiment, after configuration, a dual-portvirtual router configuration can be provided such that a subnet managersees a proper end node, signifying an end of the subnet that the subnetmanager is responsible for.

In accordance with an embodiment, at a switch 1220 in subnet A 1201, aswitch port can be connected (i.e., logically connected) to a routerport 1211 in a virtual router 1210 via a virtual link 1223. The virtualrouter 1210 (e.g., a dual-port virtual router), which while shown asbeing external to the switch 1220 can, in embodiments, be logicallycontained within the switch 1220, can also comprise a second routerport, router port II 1212. In accordance with an embodiment, a physicallink 1203, which can have two ends, can connect the subnet A 1201 viafirst end of the physical link with subnet B 1202 via a second end ofthe physical link, via router port II 1212 and router port II 1232,contained in virtual router 1230 in subnet B 1202. Virtual router 1230can additionally comprise router port 1231, which can be connected(i.e., logically connected) to switch port 1241 on switch 1240 via avirtual link 1233.

In accordance with an embodiment, a subnet manager (not shown) on subnetA can detect router port 1211, on virtual router 1210 as an end point ofthe subnet that the subnet manager controls. The dual-port virtualrouter abstraction can allow the subnet manager on subnet A to deal withsubnet A in a usual manner (e.g., as defined per the InfiniBandspecification). At the subnet management agent level, the dual-portvirtual router abstraction can be provided such that the SM sees thenormal switch port, and then at the SMA level, the abstraction thatthere is another port connected to the switch port, and this port is arouter port on a dual-port virtual router. In the local SM, aconventional fabric topology can continue to be used (the SM sees theport as a standard switch port in the topology), and thus the SM seesthe router port as an end port. Physical connection can be made betweentwo switch ports that are also configured as router ports in twodifferent subnets.

In accordance with an embodiment, the dual-port virtual router can alsoresolve the issue that a physical link could be mistakenly connected tosome other switch port in the same subnet, or to a switch port that wasnot intended to provide a connection to another subnet. Therefore, themethods and systems described herein also provide a representation ofwhat is on the outside of a subnet.

In accordance with an embodiment, within a subnet, such as subnet A, alocal SM determines a switch port, and then determines a router portconnected to that switch port (e.g., router port 1211 connected, via avirtual link 1223, to switch port 1221). Because the SM sees the routerport 1211 as the end of the subnet that the SM manages, the SM cannotsend discovery and/or management messages beyond this point (e.g., torouter port II 1212).

In accordance with an embodiment, the dual-port virtual router describedabove provides a benefit that the dual-port virtual router abstractionis entirely managed by a management entity (e.g., SM or SMA) within thesubnet that the dual-port virtual router belongs to. By allowingmanagement solely on the local side, a system does not have to providean external, independent management entity. That is, each side of asubnet to subnet connection can be responsible for configuring its owndual-port virtual router.

In accordance with an embodiment, in a situation where a packet, such asan SMP, is addressed to a remote destination (i.e., outside of the localsubnet) arrives local target port that is not configured via thedual-port virtual router described above, then the local port can returna message specifying that it is not a router port.

Many features of the present invention can be performed in, using, orwith the assistance of hardware, software, firmware, or combinationsthereof. Consequently, features of the present invention may beimplemented using a processing system (e.g., including one or moreprocessors).

FIG. 13 shows a method for supporting dual-port virtual router in a highperformance computing environment, in accordance with an embodiment. Atstep 1310, the method can provide at one or more computers, includingone or more microprocessors, a first subnet, the first subnet comprisinga plurality of switches, the plurality of switches comprising at least aleaf switch, wherein each of the plurality of switches comprise aplurality of switch ports, a plurality of host channel adapters, eachhost channel adapter comprising at least one host channel adapter port,a plurality of end nodes, wherein each of the end nodes are associatedwith at least one host channel adapter of the plurality of host channeladapters, and a subnet manager, the subnet manager running on one of theplurality of switches and the plurality of host channel adapters.

At step 1320, the method can configure a switch port of the plurality ofswitch ports on a switch of the plurality of switches as a router port.

At step 1330, the method can logically connect the switch portconfigured as the router port to a virtual router, the virtual routercomprising at least two virtual router ports.

Ensuring Unique Multicast Across Multiple Connected Subnets

In accordance with an embodiment, a system can support multicastrouting. Multicast routing is a one-to-many/many-to-many communicationparadigm designed to simplify and improve the efficiency ofcommunication between a set of end nodes (e.g., hosts, virtual machines. . . etc.).

In accordance with an embodiment, in a single subnet system, a multicastgroup can be identified by a unique GID. End nodes can be joined to orleave a multicast group through a management action where the nodesupplies the identity (GID) for each port that will participate. Thisinformation can be distributed to the switches. Each switch isconfigured with routing information for the multicast traffic whichspecifies all of the local switch ports where the packet is addressed totravel. Care is taken to assure there are no loops (i.e., a singlespanning tree such that a packet is not forwarded to a switch thatalready processed that packet).

In accordance with an embodiment, the node uses the multicast LID andGID in all packets it sends to that multicast group. When a switchreceives a multicast packet (i.e., a packet with a multicast LID in thepacket's DLID field) it replicates the packet and sends it out to eachof the designated ports except the arrival port. In this fashion, eachcascaded switch replicates the packet such that the packet arrives onlyonce at every subscribed end node.

In accordance with an embodiment, a channel adapter may limit the numberof QPs that can register for the same multicast address. The channeladapter distributes multicast packets to QPs registered for thatmulticast address. A single QP can be registered for multiple addressesfor the same port but if a consumer wishes to receive multicast trafficon multiple ports it needs a different QP for each port. The channeladapter recognizes a multicast packet by the packet's DLID or by thespecial value in the packet's Destination QP field and routes the packetto the QPs registered for that address and port.

In accordance with an embodiment, multicast routing withininterconnected subnets requires a global view and a single globalspanning tree in order to ensure that a single multicast packet is notdelivered more than once to each potential receiver end-point.

In accordance with an embodiment, by enforcing that incoming (i.e.,incoming on a router port of a subnet) multicast packets have SGIDs(source global identifiers) that correspond to a restricted set ofsource subnet numbers when entering the ingress router ports to a localsubnet, it is possible to ensure that multicast packets sent from onesubnet are never returned to the same subnet through a different set ofconnected router ports (i.e., avoid looping multicast packets).

In accordance with an embodiment, in a situation with two directlyconnected subnets, such loop avoidance can be achieved by enforcing thatall incoming multicast packets have the source subnet prefix thatcorresponds to the neighbor subnet. Put another way, in order to enforceloop avoidance, MC packets received at an ingress port of a routerwithin a subnet can be checked to determine if the inbound MC packetcomprises a subnet prefix that is the same as the subnet prefix of thesubnet at which the MC packet is received. If so, the packet can bedropped at the router in order to avoid a loop.

FIG. 14 illustrates a system for supporting unique multicast forwardingacross multiple subnets in a high performance computing environment, inaccordance with an embodiment.

In accordance with an embodiment, a system can comprise two or moresubnets, such as subnet A 1400 and subnet B 1410. Subnets A and B cancomprise a number of end nodes, respectively, such as end node 1401, endnode 1402, end node 1411, and end node 1412. In an effort forsimplicity, the configuration of the end nodes is not explicitly shownin the figure. One of ordinary skill in the art will understand that theend nodes can comprise a number of configurations, such as thosedescribed above in relation to physical end nodes, virtual machines,virtual switches, and the like. Subnet A can additionally comprise anumber of switches, representatively shown as switches 1404-1407, and anumber of routers, such as routers 1403 and 1408. Subnet B can likewiseadditionally comprise a number of switches, representatively shown asswitches 1414-1417, and a number of routers, such as routers 1413 and1418. It is to be understood that the routers, although shown asseparate components, can also comprise a virtual router, such as thedual-port virtual router configuration.

For example, in accordance with an embodiment, after configuration, adual-port virtual router configuration can be provided such that asubnet manager sees a proper end node, signifying an end of the subnetthat the subnet manager is responsible for. In accordance with anembodiment, at a switch 1404 in subnet A 1400, a switch port can beconnected (i.e., logically connected) to a router port in a virtualrouter 1405 via a virtual link. The virtual router 1403 (e.g., adual-port virtual router), which while shown as being external to theswitch 1404 can, in embodiments, be logically contained within theswitch 1404, can also comprise a second router port, router port II. Inaccordance with an embodiment, a physical link, which can have two ends,can connect the subnet A 1400 via first end of the physical link withsubnet B 1401 via a second end of the physical link, via router ports atthe routers in the different subnets.

In accordance with an embodiment, end node 1412 can initiate an MCpacket 1450. The MC packet 1450 can be associated with a number ofdifferent elements (not shown), such as a MCG (multicastgroup—representing a list of addresses to which the MC packet needs tobe distributed), as well as an SGID (source global identifier). TheSGID, in addition to indicating the source of the MC packet 1450,additionally comprises a source subnet identifier, identifying thesource of the MC packet as subnet B 1410.

In accordance with an embodiment, end nodes can be joined to or leave amulticast group through a management action where the node supplies theLID for each port that will participate. This information can bedistributed to the switches. Each switch is configured with routinginformation for the multicast traffic which specifies all of the portswhere the packet is addressed to travel. Care is taken to assure thereare no loops (i.e., a single spanning tree such that a packet is notforwarded to a switch that already processed that packet).

In accordance with an embodiment, the node uses the multicast LID andGID in all packets it sends to that multicast group. When a switchreceives a multicast packet (i.e., a packet with a multicast LID in thepacket's DLID field) it replicates the packet and sends it out to eachof the designated ports except the arrival port. In this fashion, eachcascaded switch replicates the packet such that the packet arrives onlyonce at every subscribed end node.

In accordance with an embodiment, each MC packet is originated from asource node/host—that source comprises a layer 3 source address, whichis unique source address, and also has a layer 3 destination addresseswhich represents the group (128 bit global id). A MC packet is a packetof a special class that comprises a global router header regardless ofwhether it is only sent within a local subnet or if it is sentinter-subnet. In accordance with an embodiment, the source addresscomprises the source subnet number of the originating node. In the caseof directly connected subnets, any packet received from a port connectedto the remote subnet can have a source address representing the SubnetID of the peer subnet.

In accordance with an embodiment, as shown in FIG. 15, which illustratesa system for supporting unique multicast forwarding across multiplesubnets in a high performance computing environment, in accordance withan embodiment, once the MC packet arrives at a switch, such as switch1417, the switch, as determined by the existing routing tables and MCGtables in memory at the switch, replicates the MC packet 1450 andaddresses it to the different locations. In the situation shown in FIG.15, the MC packet 1450 is forwarded to end node 1411, as well as acrossa link between router 1413 and router 1403, into subnet A 1400.

In accordance with an embodiment, as shown in FIG. 16, which illustratesa system for supporting unique multicast forwarding across multiplesubnets in a high performance computing environment, in accordance withan embodiment, once the MC packet arrives in subnet A 1400, the MCpacket is replicated an additional number of times. For example, switch1404 can replicate the MC packet such that the packet is addressed toend nodes 1401 and 1402. However, because the MC packet is replicatedand sent out across the paths, excluding the originating path, the MCpacket 1450 can also be addressed back to subnet B 1410 on a linkbetween router 1408 and 1418.

In accordance with an embodiment, as shown in FIG. 17, which illustratesa system for supporting unique multicast forwarding across multiplesubnets in a high performance computing environment, in accordance withan embodiment, once the MC packet arrives at an ingress port at router1418, the router 1418 can read the packet header of the MC packet 1450.Because the packet header of MC packet 1450 comprises the SGIDidentifying subnet B as the source of the MC packet, router 1418 candetermine, by, for example, comparing the source identifier of MC Packet1450 with the identity of the subnet in which router B resides, that theMC packet originated in subnet B (i.e., compare the source subnet numberof the MC packet with the subnet that the MC packet arrives at). If thedetermination reveals that the MC packet is arriving at the subnet inwhich the MC packet originated, the router can drop the MC packet so asto avoid a loop. In other words, at ingress, the router port verifiesthat the source subnet number is not the local subnet number.

FIG. 18 is a flow chart of a method for supporting unique multicastforwarding across multiple subnets in a high performance computingenvironment, in accordance with an embodiment.

At step 1810, the method can provide, at one or more computers,including one or more microprocessors, a first subnet, the first subnetcomprising one or more switches, the one or more switches comprising atleast a leaf switch, wherein each of the one or more switches comprise aplurality of switch ports, a plurality of host channel adapters, eachhost channel adapter comprising at least one host channel adapter port,a plurality of end nodes, wherein the plurality of end nodes areinterconnected via the one or more switches, and a subnet manager, thesubnet manager running on one of the one or more switches and theplurality of end nodes.

At step 1820, the method can configure a switch port of the plurality ofswitch ports on a switch of the one or more switches as a router port.

At step 1830, the method can configure a second switch port of theplurality of switch ports on a second switch of the one or more switchesas a second router port.

At step 1840, the method can interconnect the first subnet with a secondsubnet via the router port and the second router port.

At step 1850, the method can send, from an end node of the plurality ofend nodes, a multicast packet, wherein the multicast packet comprises asource global identifier (SGID).

In accordance with an embodiment, each router port can check the SGID ofmulticast packets arriving from the peer subnet via the physical link,and discard any such multicast packets that have an SGID that representsthe same Subnet ID as the local subnet.

Inter-Subnet Control Plane Protocol for Ensuring Consistent MulticastMembership and Connectivity

In accordance with an embodiment, and as described above, a system cansupport multicast routing. Multicast routing is aone-to-many/many-to-many communication paradigm designed to simplify andimprove the efficiency of communication between a set of end nodes(e.g., hosts, virtual machines . . . etc.).

In accordance with an embodiment, systems and methods ensure thatmulticast traffic between connected subnets is handled correctly. Bythis it is meant that systems and methods can ensure that multicasttraffic between any pair of connected subnets is controlled such that amulticast packet that is received at a local router port is not sentback out on another router port back to the originating, remote subnet(i.e., akin to the above, avoiding multicast loops).

In accordance with an embodiment, certain partitions can be classifiedas “Inter Subnet Partitions” (also referred to herein as ISPs). Whensuch certain partitions are thus classified, subnet management entities(e.g., SMs or inter-subnet managers (ISMs)) can ensure that onlyproperly classified partitions are allowed to be used for data trafficto remote subnets.

In accordance with an embodiment, a global management entity, such as anInter Subnet Manager (ISM) can allocate a certain P_Key range withinwhich all ISPs can reside (i.e., any ISP in such an environment musthave a P_Key within the P_Key range as defined by then ISM). By ensuringthat ISPs are allocated from a specific P_Key range, it is possible toensure that some P_Key ranges can be used for different purposes bydifferent subnets while P_Key ranges used for ISPs are used consistentlyby all relevant subnets.

In accordance with an embodiment, by observing which end-nodes aremembers of which ISPs and correlating this with what local router portsare members of the same ISPs, the set of possible inter subnet paths canbe determined both within each local subnet as well as between connectedsubnets.

In accordance with an embodiment, by observing that directly connectedrouter ports from different subnets are both members of the same set ofISPs, it can be determined that configuration is consistent in bothsubnets without exchanging additional information between the subnets.

In accordance with an embodiment, when a SM successfully processes anMCG (multicast group) join request for an MGID associated with an ISP, alocal ISM can be notified, and the local ISM can notify any neighborISMs (i.e., ISMs in connected subnets) where the relevant ISP defineslogical inter-subnet connectivity.

In accordance with an embodiment, when an ISP based MCG has been joinedby a HCA port in each of a pair of subnets logically connected by theISP, each ISM can select one (or more) router port(s) that it can set upas member of the MCG (i.e., for forwarding outgoing MCG traffic). Thisrouter port is identified to the relevant remote ISM who can then set upthis router port to perform translation from the relevant (global) MGIDto the relevant (subnet local) MLID. When this is completed, anyrelevant MCG packet generated by an end-port (HCA) in either subnet willreach all end-port MCG members in either subnet.

In accordance with an embodiment, during exchange of communicationbetween inter-subnet managers in connected subnets, multicast groups(identified by a global multicast ID (MGID)) can be associated with anactive ISP when at least one channel adapter port in each of theconnected subnets has joined the multicast group. In such situations, anISM in each subnet can select a router port, which is part of the sameISP as the multicast group, for each relevant peer subnet that can beused to receive multicast packets from connected subnets.

In accordance with an embodiment, the selection of local router port bythe management entity can be based on the router port (a router portthat is within a set of router ports that currently connects therelevant subnets) having the correct ISP membership (i.e., being atleast a member of the same ISP as the multicast group), and that theexternal link supports the MTU defined for the multicast group.

In accordance with an embodiment, information about active multicastgroups and selected multicast receiver ports can be forwarded from eachlocal subnet (master ISM) to each relevant peer subnet.

In accordance with an embodiment, when a multicast group is active intwo connected subnets, the inter-subnet multicast traffic for this MGIDcan be enabled in each subnet in the following way. First, a the localrouter port that has been selected as the router port to be used for therelevant multicast group can have the incoming address map set up forthe relevant MGID. Next, if only a single local router port is used forboth incoming and outgoing traffic for the relevant MGID, then it willbe joined as full member of the relevant multicast group.

In accordance with an embodiment, when only one router port is selectedas a full member (send and receive) for the multicast traffic of themulticast group, enforcement of multicast loop can be provided. Becausethe IB specification defines that a MC packet transferred on a linkcannot be transferred back on the same link, once an incoming (from aconnected subnet) MC packet enters a local subnet via the selectedrouter port, the MC packet cannot then leave the subnet via the samerouter port. Because only a single router port was selected as beingcapable of handling the MC packet, no other router port in the subnetcan then pass the MC packet back to the originating subnet.

In accordance with an embodiment, in the case where there are two routerports selected as being able to handle the MC packets from a MC group, asubnet management entity can enforce MC loop avoidance by designating arouter port responsible for incoming MC traffic as “send only,” whilethe other router port can be configured as a full member.

FIG. 19 illustrates a system for supporting an inter-subnet controlplane protocol for ensuring consistent multicast membership andconnectivity in a high performance computing environment, in accordancewith an embodiment.

In accordance with an embodiment, a system can comprise two or moresubnets, such as subnet A 1400 and subnet B 1410. Subnets A and B cancomprise a number of end nodes, respectively, such as end node 1401, endnode 1402, end node 1411, and end node 1412. In an effort forsimplicity, the configuration of the end nodes is not explicitly shownin the figure. One of ordinary skill in the art will understand that theend nodes can comprise a number of configurations, such as thosedescribed above in relation to physical end nodes, virtual machines,virtual switches, and the like. Subnet A can additionally comprise anumber of switches, representatively shown as switches 1404-1407, and anumber of routers, such as routers 1403 and 1408. Subnet B can likewiseadditionally comprise a number of switches, representatively shown asswitches 1414-1417, and a number of routers, such as routers 1413 and1418. It is to be understood that the routers, although shown asseparate components, can also comprise a virtual router, such as thedual-port virtual router configuration.

For example, in accordance with an embodiment, after configuration, adual-port virtual router configuration can be provided such that asubnet manager sees a proper end node, signifying an end of the subnetthat the subnet manager is responsible for. In accordance with anembodiment, at a switch 1404 in subnet A 1400, a switch port can beconnected (i.e., logically connected) to a router port in a virtualrouter 1405 via a virtual link. The virtual router 1403 (e.g., adual-port virtual router), which while shown as being external to theswitch 1404 can, in embodiments, be logically contained within theswitch 1404, can also comprise a second router port, router port II. Inaccordance with an embodiment, a physical link, which can have two ends,can connect the subnet A 1400 via first end of the physical link withsubnet B 1401 via a second end of the physical link, via router ports atthe routers in the different subnets.

In accordance with an embodiment, a SM (not shown) within subnet A 1400can process a multicast group join request from a local end node (e.g.,end node 1401 or 1402) where the multicast group's global ID is, or isto be associated with an ISP. Upon successful join, a local ISM, such asISM 1901, can be notified, and the local ISM can notify any neighborISMs (i.e., ISMs in connected subnets, such as ISM 1902).

In accordance with an embodiment, each ISM can select a router port thatit can set up as member of the MCG (i.e., for forwarding outgoing MCGtraffic). This is shown in the figure as selection 1910, by ISM 1901 ofa router port at router 1403. This router port is identified to therelevant remote ISM who can then set up the relevant router port in itslocal subnet (e.g., in router 1413) to perform translation from therelevant (global) MGID to the relevant (subnet local) MLID. Whenconfiguration of both outbound and inbound forwarding for the relevantMCG is completed in both subnets, any relevant MCG packet generated byan end-node in either subnet, such as end node 1411 or 1412 in subnet B,can reach all end-port members in the relevant MCG in either subnet.

In accordance with an embodiment, end node 1412 can initiate a MC packet1950, which can be targeting the relevant multicast group. As the ISMs1901 and 1902 have exchanged information related to which router portshave been configured to accept MC packets within the MC group, the MCpacket can be directed to the selected router port within router 1403,as shown in FIG. 20. FIG. 20 illustrates a system for supporting aninter-subnet control plane protocol for ensuring consistent multicastmembership and connectivity in a high performance computing environment,in accordance with an embodiment.

In accordance with an embodiment, although not shown, within FIG. 20, itis determined that ISM 1902 selected a router port at router 1413 asbeing responsible for the MC group traffic, which is why the MC packet1950 is shown as being passed between router ports between routers 1413and 1403.

FIG. 21 illustrates a system for supporting an inter-subnet controlplane protocol for ensuring consistent multicast membership andconnectivity in a high performance computing environment, in accordancewith an embodiment.

More specifically, in accordance with an embodiment, FIG. 21 illustratesthe multicast loop avoidance when an ISM selects one router port asbeing responsible for the MC group traffic. As ISM 1901 selected arouter port at router 1403 as being responsible for MC group trafficthat comprises MC packet 1950, once the selected router port has beenpassed into the subnet A from the selected router port, the MC packetcannot utilize a router port at router 1408 (as the router is notconfigured with the relevant MCG—the other router port (1408) may stillbe a member of the relevant ISP, but not the same MCG), nor can the MCpacket be routed back through the selected router port at router 1403 asthe IB specification defines that the packet cannot traverse the link inthe opposite direction.

FIG. 22 is a flow chart of a method for supporting multicast forwardingacross multiple subnets in a high performance computing environment.

At step 2210, the method can provide, at one or more computers,including one or more microprocessors, a first subnet, the first subnetcomprising one or more switches, the one or more switches comprising atleast a leaf switch, wherein each of the one or more switches comprise aplurality of switch ports, a plurality of end nodes, wherein theplurality of end nodes are interconnected via the one or more switches,a subnet manager, the subnet manager running on one of the one or moreswitches and the plurality of end nodes, and an inter-subnet manager,the inter-subnet manager running on one of the one or more switches andthe plurality of end nodes.

At step 2220, the method can configure a switch port of the plurality ofswitch ports on a switch of the one or more switches as a router port.

At step 2230, the method can configure a second switch port of theplurality of switch ports on a second switch of the one or more switchesas a second router port.

At step 2240, the method can interconnect the first subnet with a secondsubnet via the router port and the second router port.

At step 2250, the method can set up a multicast group within the firstsubnet, the multicast group comprising a multicast global identifier(MGID), the MGID being a member of an inter-subnet partition (ISP).

Features of the present invention can be implemented in, using, or withthe assistance of a computer program product which is a storage medium(media) or computer readable medium (media) having instructions storedthereon/in which can be used to program a processing system to performany of the features presented herein. The storage medium can include,but is not limited to, any type of disk including floppy disks, opticaldiscs, DVD, CD-ROMs, microdrive, and magneto-optical disks, ROMs, RAMs,EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or opticalcards, nanosystems (including molecular memory ICs), or any type ofmedia or device suitable for storing instructions and/or data.

Stored on any one of the machine readable medium (media), features ofthe present invention can be incorporated in software and/or firmwarefor controlling the hardware of a processing system, and for enabling aprocessing system to interact with other mechanism utilizing the resultsof the present invention. Such software or firmware may include, but isnot limited to, application code, device drivers, operating systems andexecution environments/containers.

Features of the invention may also be implemented in hardware using, forexample, hardware components such as application specific integratedcircuits (ASICs). Implementation of the hardware state machine so as toperform the functions described herein will be apparent to personsskilled in the relevant art.

Additionally, the present invention may be conveniently implementedusing one or more conventional general purpose or specialized digitalcomputer, computing device, machine, or microprocessor, including one ormore processors, memory and/or computer readable storage mediaprogrammed according to the teachings of the present disclosure.Appropriate software coding can readily be prepared by skilledprogrammers based on the teachings of the present disclosure, as will beapparent to those skilled in the software art.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample, and not limitation. It will be apparent to persons skilled inthe relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have often been arbitrarily defined herein for theconvenience of the description. Alternate boundaries can be defined solong as the specified functions and relationships thereof areappropriately performed. Any such alternate boundaries are thus withinthe scope and spirit of the invention.

The foregoing description of the present invention has been provided forthe purposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise forms disclosed. Thebreadth and scope of the present invention should not be limited by anyof the above-described exemplary embodiments. Many modifications andvariations will be apparent to the practitioner skilled in the art. Themodifications and variations include any relevant combination of thedisclosed features. The embodiments were chosen and described in orderto best explain the principles of the invention and its practicalapplication, thereby enabling others skilled in the art to understandthe invention for various embodiments and with various modificationsthat are suited to the particular use contemplated. It is intended thatthe scope of the invention be defined by the following claims and theirequivalents.

What is claimed is:
 1. A system for supporting multicast forwardingacross multiple subnets in a high performance computing environment,comprising: one or more microprocessors; a first subnet, the firstsubnet comprising a plurality of switches, a plurality of end nodes, asubnet manager, and an inter-subnet manager; wherein a switch port of afirst switch of the plurality of switches is configured, by the subnetmanager, as a first router port; wherein a switch port of a secondswitch of the plurality of switches is configured, by the subnetmanager, as a second router port; wherein the first subnet isinterconnected with a second subnet via a first link connected to thefirst router port and a second link connected to the second router port,the second subnet comprising an inter-subnet manager of the secondsubnet; wherein a multicast group is defined within the first subnet;wherein the inter-subnet manager configures the first router port to bea full member of the multicast group, wherein the inter-subnet managerprovides an identification of the configured first router port to theinter-subnet manager of the second subnet; wherein a multicast packet isreceived at the first router port from the second subnet, the receivedmulticast packet belonging to the multicast group, wherein, uponreceiving the multicast packet at the first router port, the multicastpacket is distributed to a set of the plurality of end nodes in thefirst subnet; wherein the inter-subnet manager of the second subnetdirects the multicast packet to the first router port based on theprovided identification of the configured first router port; andwherein, upon the multicast packet being received at the first routerport, based upon the configuring the first router port as a full memberof the multicast group, the first switch and the second switch preventthe multicast packet from being transmitted to the second subnet, via,respectively, the first link and the second link.
 2. The system of claim1, wherein the plurality of end nodes comprises a virtual machine, thefirst subnet further comprising: a host channel adapters, wherein thehost channel adapter comprises at least one virtual function, and atleast one physical function; a hypervisor, wherein the hypervisor isassociated with the host channel adapter; and wherein the virtualmachine is associated with the at least one virtual function.
 3. Thesystem of claim 1, wherein, upon the configuration, by the inter-subnetmanager, of the first router port as a full member of the multicastgroup, the first router port is configured to receive and send multicastpackets associated with the multicast group.
 4. The system of claim 1,wherein, upon the configuration, by the inter-subnet manager, of thefirst router port as a full member of the multicast group, the secondrouter port is configured to drop multicast packets of the multicastgroup.
 5. The system of claim 1, wherein the second subnet furthercomprises: a plurality of switches of the second subnet, a plurality ofend nodes of the second subnet, and a subnet manager of the secondsubnet.
 6. The system of claim 1, wherein the set of the plurality ofend nodes to which the multicast packet is distributed are members ofthe multicast group.
 7. A method for supporting multicast forwardingacross multiple subnets in a high performance computing environment,comprising: providing, at one or more computers, including one or moremicroprocessors, a first subnet, the first subnet comprising a pluralityof switches, a plurality of end nodes, a subnet manager, and aninter-subnet manager; configuring, by the subnet manager, a switch portof a first switch of the plurality of switches as a first router port;configuring, by the subnet manager, a switch port of a second switch ofthe plurality of switches as a second router port; interconnecting thefirst subnet with a second subnet via a first link connected to thefirst router port and a second link connected to the second router port,the second subnet comprising an inter-subnet manager of the secondsubnet; defining a multicast group within the first subnet; configuring,by the inter-subnet manager, the first router port to be a full memberof the multicast group, wherein the inter-subnet manager provides anidentification of the configured first router port to the inter-subnetmanager of the second subnet; receiving a multicast packet at the firstrouter port from the second subnet, the received multicast packetbelonging to the multicast group, wherein, upon receiving the multicastpacket at the first router port, the multicast packet is distributed toa set of the plurality of end nodes in the first subnet; wherein theinter-subnet manager of the second subnet directs the multicast packetto the first router port based on the provided identification of theconfigured first router port; and wherein, upon the multicast packetbeing received at the first router port, based upon the configuring thefirst router port as a full member of the multicast group, the firstswitch and the second switch prevent the multicast packet from beingtransmitted to the second subnet, via, respectively, the first link andthe second link.
 8. The method of claim 7, wherein the plurality of endnodes comprises a virtual machine, the first subnet further comprising:a host channel adapter, wherein the host channel adapter comprises atleast one virtual function, and at least one physical function; ahypervisor, wherein the hypervisor is associated with the host channeladapter; and wherein the virtual machine is associated with the at leastone virtual function.
 9. The method of claim 7, further comprising: uponthe configuration, by the inter-subnet manager, of the first router portto be a full member of the multicast group, configuring the first routerport to receive and send multicast packets associated with the multicastgroup.
 10. The method of claim 7, further comprising: upon theconfiguration, by the inter-subnet manager, of the first router port asa full member of the multicast group, configuring the second router portto drop multicast packets of the multicast group.
 11. The method ofclaim 7, wherein the second subnet further comprises: a plurality ofswitches of the second subnet, a plurality of end nodes of the secondsubnet, and a subnet manager of the second subnet.
 12. The method ofclaim 7, further comprising: wherein the set of the plurality of endnodes to which the multicast packet is distributed are members of themulticast group.
 13. A non-transitory computer readable storage medium,including instructions stored thereon for supporting multicastforwarding across multiple subnets in a high performance computingenvironment, which when read and executed by one or more computers causethe one or more computers to perform steps comprising: providing, at oneor more computers, including one or more microprocessors, a firstsubnet, the first subnet comprising a plurality of switches, a pluralityof end nodes, a subnet manager, and an inter-subnet manager;configuring, by the subnet manager, a switch port of a first switch ofthe plurality of switches as a first router port; configuring, by thesubnet manager, a switch port of a second switch of the plurality ofswitches as a second router port; interconnecting the first subnet witha second subnet via a first link connected to the first router port anda second link connected to the second router port, the second subnetcomprising an inter-subnet manager of the second subnet; defining amulticast group within the first subnet; configuring, by theinter-subnet manager, the first router port to be a full member of themulticast group, wherein the inter-subnet manager provides anidentification of the configured first router port to the inter-subnetmanager of the second subnet; receiving a multicast packet at the firstrouter port from the second subnet, the received multicast packetbelonging to the multicast group, wherein, upon receiving the multicastpacket at the first router port, the multicast packet is distributed toa set of the plurality of end nodes in the first subnet; wherein theinter-subnet manager of the second subnet directs the multicast packetto the first router port based on the provided identification of theconfigured first router port; and wherein, upon the multicast packetbeing received at the first router port, based upon the configuring thefirst router port as a full member of the multicast group, the firstswitch and the second switch prevent the multicast packet from beingtransmitted to the second subnet, via, respectively, the first link andthe second link.
 14. The non-transitory computer readable storage mediumof claim 13, wherein the plurality of end nodes comprises a virtualmachine, the first subnet further comprising: a host channel adapter,wherein the host channel adapter comprises at least one virtualfunction, and at least one physical function; a hypervisor, wherein thehypervisor is associated with the host channel adapter; and wherein thevirtual machine is associated with the at least one virtual function.15. The non-transitory computer readable storage medium of claim 13, thesteps further comprising: upon the configuration, by the inter-subnetmanager, of the first router port to be a full member of the multicastgroup, configuring the first router port to receive and send multicastpackets associated with the multicast group.
 16. The non-transitorycomputer readable storage medium of claim 13, the steps furthercomprising: upon the configuration, by the inter-subnet manager, of thefirst router port as a full member of the multicast group, configuringthe second router port to drop multicast packets of the multicast group.17. The non-transitory computer readable storage medium of claim 13,wherein the second subnet further comprises: a plurality of switches ofthe second subnet, a plurality of end nodes of the second subnet, and asubnet manager of the second subnet.